An image forming apparatus of the related art may employ a light-emitting diode (LED) head. The LED head includes a plurality of LED elements disposed in a main-scanning direction of the LED head. A plurality of LED heads can be disposed in an image forming apparatus for recording images of cyan (C), magenta (M), yellow (Y), and black (K) colors.
When the image forming apparatus prints an image on a sheet, image density may be non-uniform in the main scanning direction, thus posing a problem of deteriorating image quality. The non-uniform image density in the main-scanning direction is mainly caused by variations in mechanical accuracy of the position of a photoreceptor drum and a development roller (e.g., magnetic roller). The variations cause an interval (gap) between the photoreceptor drum and the development roller to be different in the longitudinal direction of the photoreceptor drum and the development roller, thus widening the gap at a central part in the longitudinal direction. In addition, non-uniform image density can also be caused by the photoreceptor drum and the LED head being dislocated in the longitudinal direction.
A regulation member that faces the development roller and regulates the thickness of a layer of a developer is disposed at a predetermined interval with respect to the development roller. The regulation member regulates the layer of the developer on the outer surface of the development roller so that the developer layer does not become excessively thick. However, the image density becomes non-uniform when the development roller bends to decrease the amount of the developer that adheres to the central part of the development roller in the longitudinal direction. In addition, the regulation member bends to change the amount of the developer transported on the development roller, thus causing the non-uniform image density.
Techniques to compensate for the non-uniform image density include improving accuracy and rigidity of components in a part where the gap is formed between the photoreceptor drum and the development roller, or adjusting magnetic power of the development roller in the longitudinal direction. However, these techniques increase cost.
Another technique involves controlling the intensity of light emitted from the LED to correct the non-uniform image density. For example, an image is read, analyzed, and is computationally processed to give feedback to each LED element for correcting change in the intensity of light emitted from the LED element due to temperature change. However, such a technique increases circuit complexity and cost.